1. Field of the Invention
The present invention relates to a syringe barrel and hypodermic needle assembly, and an assembly of syringe barrels. More particularly, the present invention relates to a syringe barrel and hypodermic needle assembly wherein the hypodermic needle assembly contains a rearwardly facing cannula capable of piercing a barrier within the syringe barrel and to an assembly of a plurality of syringe barrels and integral web portions.
2. Description of the Prior Art
Generally speaking, a hypodermic syringe consists of a cylindrical barrel, most commonly made of plastic or glass, with a distal end adapted to be connected to a hypodermic needle and a proximal end adapted to receive a stopper and plunger rod assembly. One of the purposes of the stopper is to provide a relatively air-tight seal between itself and the syringe barrel so that movement of the stopper up and down the barrel will cause liquid, blood or other fluids to be drawn into or forced out of the syringe through the distal end. The stopper is moved along the syringe barrel by applying axial force to a rigid plunger rod which is connected to the stopper and is sufficiently long to be accessible outside of the barrel. An example of a rigid barrel syringe is illustrated in U.S. Pat. No. 4,430,080 to Pasquini et al.
Also known to the art are hypodermic syringes having a flexible barrel portion, usually made of thermoplastic material, with a distal end adapted to be connected to a hypodermic needle. With a hypodermic needle attached, the user of a flexible barrel hypodermic syringe assembly may expel the medication by manually squeezing the flexible barrel portion forcing the medication through the hypodermic needle cannula and into the patient. A hypodermic syringe unit having a flexible barrel portion is illustrated in U.S. Pat. No. 2,680,440 to Fox.
A wide variety of injectable medications, or medications which can be rendered into injectable form by the addition of a diluent, are prefilled in rigid and flexible syringe barrel assemblies by pharmaceutical manufacturers, contract packagers, and the like. The medication containing syringes often sit many weeks or months before administration of medication to the patient. Under these circumstances, it is desirable to isolate the medication from the environment as thoroughly as possible. This task is more easily accomplished at the proximal end of the syringe where, in the case of a rigid syringe, a resilient rubber stopper can effectively seal the barrel. In the case of a flexible barrel syringe, the proximal end may be sealed shut, for example, by heat sealing, after the syringe is filled with medication. At the distal end of the syringe barrel the problem of isolating the medication from the environment is more difficult to solve. In rigid barrel syringes, it is common practice to seal the tip at the distal end of the syringe with elastomeric tip caps as described in U.S. Pat. No. 4,444,310 to Odell wherein the tip cap is removed at the time of use and a hypodermic needle assembly is placed over the syringe tip. In a rigid barrel syringe, the medication may also be isolated by placing an additional stopper in the syringe barrel so that the medication is contained between two resilient stoppers. When a stopper is used to provide needle isolation, additional structure in the syringe barrel is necessary to allow fluid to bypass the distal-most stopper. An example of this structure is illustrated in U.S. Pat. No. 3,330,282 to Visser et al.
In prefilled flexible barrel syringes, needle isolation may be accomplished by occluding the lumen of the cannula with a removable plug as illustrated in the above-mentioned patent to Fox. Also, needle isolation may be accomplished by providing a barrier between the medication and the syringe tip, and a hypodermic needle having a dual pointed cannula. At the time of use, the hypodermic needle may be moved in a rearward direction so that the rearmost cannula pierces the barrier establishing fluid communication between the chamber containing the medication and the hypodermic cannula. Such a syringe is illustrated in U.S. Pat. No. 4,018,222 to McAleer et al. A pierceable barrier design along the lines taught by McAleer et al, is advantageous with respect to its ability to isolate the medication from the environment, however, it has deficiencies in that the two-pointed cannula may be inadvertently activated by pressure on the needle shield which forces the cannula through the barrier.
Problems also exist in prefilling rigid or flexible syringe barrel. When filling, for example, thousands of syringe barrels, each of these syringe barrels must be delivered to a filling station, filled and then sealed. If the filling station contains multiple filling nozzles all of the syringe barrels in the area must be spaced appropriately so that each is in the proper position with respect to the filling nozzles, and then the syringe barrels are moved as a group to a sealing station which provides for sealing of the proximal ends of the barrels. A rigid barrel syringe may be sealed via introduction of a stopper into the barrel and a flexible barrel syringe may be sealed by compressing the proximal end of the barrel shut and applying heat energy to seal this end shut. One method of accomplishing multiple unit filling and sealing is to place the syringe barrels in a fixture which holds the syringe barrels at a predetermined distance from each other so that all the barrels in the fixture will be properly aligned with the filling station nozzles and, also, the subsequent sealing operation may be performed with the syringe barrels properly positioned. At the end of the operation the individual syringe barrels must be removed from the fixture so that the fixture may be returned and used again. This is a tedious operation requiring care to avoid contamination of the fixtures by spilled medication.
Rigid and flexible barrel syringe assemblies for use with prefilled medication, having structure for isolation of the medication from the environment, and methods of prefilling have been addressed by the prior art, as alluded to above. However, there is still a need for simple, straightforward, reliable, easily fabricated syringe assemblies for the storage and administration of medications. It is desirable that the syringe barrel effectively isolates the hypodermic needle cannula from the medication and the syringe assembly is easily activated, while being difficult to activate inadvertently. It is also desirable to have a group of syringes assembled in a configuration which will eliminate the use of separate fixtures during the prefilling operation.